This book constitutes the proceedings of the 44th International Conference on Application and Theory of Petri Nets and Concurrency, PETRI NETS 2023, which took place in Lisbon, Portugal, in June 2023.  The 21 full papers included in this book were carefully reviewed and selected from 47 submissions. They were organized in topical sections as follows: Process mining; semantics; tools; verification; timed models; model transformation. The book also includes two invited talks in full paper length.